Protocol Independent Multicast (PIM) is a widely deployed multicast protocol. As defined in Request for Comments (RFC) 7761 of the Internet Engineering Task Force (IETF), a PIM designated router (DR) election is performed in each shared local area network (LAN). A PIM DR is responsible for creating a multicast routing tree upstream. There are many network events, which could initiate a PIM DR re-election. Network events that would trigger DR re-election may be classified into non-deterministic events and deterministic network events. Non-limiting examples of non-deterministic network events include a router, designated as PIM DR, restarting due to power failure or any other hardware failure, which cannot be predicted in advance, or an interface failure. Non-limiting examples of deterministic network events include a router, designated as a PIM DR, going in to maintenance mode, a new router coming up in a network, or a configuration change (e.g., change in priority of the current PIM DR or another one of the PIM routers in the LAN).
Currently, when a PIM router relinquishes its PIM DR role, the PIM router generally: lowers its priority (statically or dynamically), or sends a PIM Hello message with zero hold-time leading to a DR re-election taking place; and stops forwarding traffic. Meanwhile, the newly elected PIM DR starts building a multicast routing tree which takes time, so that traffic is lost while the multicast routing tree is being built.